In advanced microelectronic chips, structures referred to as back-end-of-line (BEOL) metallization employ several layers of metal interconnections each separated by a dielectric layer. At the present time, the dielectric typically employed is made of sputtered quartz which has a dielectric constant of about 3.9. However, in order to reduce signal delays in chips for the future, it will be necessary to reduce the dielectric constant so that the capacitance of the metallic layers will be reduced. Much work is presently being done in attempts to replace the quartz with various polyimides. The polyimides typically have a dielectric constant that is at least about 2.8. The polyimides are generally provided onto a chip by wet spin-on techniques followed by subsequent drying at elevated temperatures. However, wet-processing, spin-on and drying processing are not especially desirable since such techniques are difficult to control and tend to employ organic solvents that are undesirable from an environmental viewpoint.
Fluorinated polymeric materials such as poly(tetrafluoroethylene)(PTFE) are attractive candidates for advanced electronic packaging applications because of their relatively low dielectric constants, excellent chemical stability, low solvents/moisture absorption and excellent thermal stability. However, because of their relative chemical inertness and hydrophobic nature, these halogenated polymeric materials are difficult to process into electronic packaging structures. The lack of effective processing techniques has inhibited the exploitation of these materials by the electronics industry.
Although there have been various suggestions to produce films of polymeric fluorocarbon by plasma polymerization, the films formed would not be suitable as an insulating layer in integrated circuits since such prior films lack at least one characteristic necessary for providing a suitable dielectric or insulating layer. For instance, many of the prior suggested films inherently include metallic particles deposited during the plasma processing.